The fundamental steps in photographic processing include a color developing step and a silver removal step. In the color developing step, photographic color developing compositions are used to process color photographic materials such as color photographic films (including motion picture films) and papers to provide the desired color images. Such compositions generally contain color developing agents [for example 4-amino-3-methyl-N-(.beta.-methane sulfonamidoethyl)aniline and other p-phenylenediamines] as reducing agents to react with suitable color forming couplers in the color photographic materials to form the desired dyes. However, such color developing agents are susceptible to oxidation by dissolved oxygen. Therefore, an antioxidant is conventionally included in the color developer compositions to preserve the oxidation state of the color developing agent and thereby maintain useful color developer activity.
Color developing compositions are carefully formulated with various additives to overcome various problems besides the problems arising with color developing agent oxidation. Thus, metal ions, various sequestering agents, surfactants and other components have been added over the years to provide the stability and photographic activity that is critical to the industry.
One problem that is a concern in the industry is the formation of "tar" in and from the color developing composition. Tar has been variously defined as deposits of "polymeric oxidized developer" (see U.S. Pat. No. 5,786,134 of Nair et al) as relating to motion picture print films, and as the results of inadequate dissolution or mixing of benzyl alcohol as described in U.S. Pat. No. 4,414,307 (Kapecki et al). Basically, this undesirable substance appears to be products of the degradation of the color developing agents. The effect of tar on the processed photographic materials is a loss of image detail during viewing. This is especially noticeable when motion picture films are projected onto wide screens. In addition, the effects of tar buildup in the photographic processing lab include clogged filters and plumbing, and dirtier processing tanks, resulting in frequent downtime for cleaning. Thus, tar reduction is a continuing goal of the photographic industry in an effort to improve image quality of color images of all types and sizes.
The industry has addressed this problem of tar formation in various ways. A solution to the problem is merely to replace the processing solutions frequently. Thus, the photographic processing operators would discard color developing solutions frequently to remove the unwanted by-products that result in tar and thereby avoid more tedious cleaning routines. This can be quite expensive in time and labor, downtime, and in the cost of processing solutions.
Photographic processing innovators in the industry have attempted to save their customers from having to do this by adjusting the color developing compositions. For example, U.S. Pat. No. 4,882,264 (Kim et al) describes the use of two or more color developing agents in combination in the color developing compositions. U.S. Pat. No. 5,786,134 (noted above) addresses changes in protective overcoats in motion picture films. Additives to the color developing compositions that are considered to reduce tar formation include poly(alkyleneimines) as described in U.S. Pat. No. 4,252,892 (Case) and solubilizing compounds for benzyl alcohol as described in U.S. Pat. No. 4,414,307 (noted above). In addition, it has been know for many years that the presence of sulfonated polystyrenes (commercially available as VERSA TL71 or TL73) in color paper developing compositions reduces tar formation as described for example in U.S. Pat. No. 5,279,930 (Green et al) and U.S. Pat. No. 5,578,430 (Fyson).
While the industry has provided some solutions to the problem of tar formation, there is continuing need to find an inexpensive means for solving the problem without the need for the customer experience expensive downtime or cleaning routines, especially during processing of motion picture films.